More than 50% of prostate cancers show specific loss of heterozygosity focused on chromosomes 16q and/or 10q, suggesting the loss of critical regulatory genes (i.e., tumor suppressor). With this in mind, a subtraction-hybridization procedure was employed to identify novel molecular markers in prostate carcinomas that allowed us to isolate low abundance mRNA species that are differentially expressed. This investigation has been focused upon the molecular and biological characterization of cDNA clones obtained by utilizing the subtraction- hybridization technique developed in the LMO using mRNA malignant human prostatic cell lines (LnCaP, Du145, PC3), each derived from tumors having varying degrees of metastasis. Over 245 cDNA clones have been screened; six of these clones range in size from 0.9 kb to 2.5 kb, and have been found to be unique by molecular sequence analysis. Screening for other novel cDNA clones is continuing. Of the unique clones identified, full- length cDNA are being isolated to determine the exons' composition of the putative novel genes. Studies of differential expression patterns of these cDNA clones and the proteins they encode, between early stage tumor tissues (A,B) and late stage samples (C,D), are in progress. Mapping experiments to locate these DNA sequences to specific chromosomes will be performed in conjunction with in situ hybridization studies on fixed tissue specimens for BPH and tumor-biopsied materials in order to assess their potential value for clinical diagnosis. These clones may prove to be useful as molecular probes in prostate cancer for determining the metastatic potential for specific stages of prostatic neoplasia. At present, there are no reliable markers that effectively predict the clinical outcome of prostatic cancer, which currently is the most frequently-occurring form of malignancy in men over the age of 65.